Wet bulb thermometer



Jan. 28, 1941. c. w. PETERSON WET BULB THERMOMETER Filed Sept. 24, 1938 1770611 1511 0mm 1.55 14/.v PET30N 63 W 9% Patented Jan. 28, 1941 PATENT OFFICE WET BULB THERMOME'IER Charles W. Peterson, West Roxbury, Mass, assignor to B. F. Sturtevant Company, Hyde Park,

Boston, Mass.

Application September 24, 1938, Serial No. 231,457-

3 Claims.

This invention relates to wet bulb thermostats and relates more particularly to thermostats for use in passenger vehicles for converting air washor systems for air conditioning, from refrigera- 5 tive; cooling to evaporative cooling cycles when the Wet bulb temperature of the outdoor air is low enough for evaporative cooling to be effective.

The ordinary wet bulb thermostat consists .of a thermometer with the upper portion of a wick around its bulb, the lower portion of the wick lying a pool of water. The water is supposed to climb up the wick through capillary action. Differential thermostats including a dry bulb thermostat. which adjusts a hygrostat to cause it to 15 respond .to wetbulb temperatures have also been used. Such thermostats have not proved entirely satisfactory for railway car service due to the difficulty of keeping the wick clean and of supplyingclean water to the wick type, and to the gmdifiiculty of maintaining the adjustment of the diiferential type.

- In some embodiment of the present invention, a thermometer has its bulb in a leather boot. A chamber in the thermostat body is ar- 25- ranged to receive water which is circulated through same at about one gallon per minute. The leather boot is connected to this chamber to receive an amount of water equal to that which is evaporated from its outer surface, the an; excess being by-passed back to the source. This new form of thermostat has functioned satisfactorily and accurately over a considerable period of time in railway passenger cars without requiring any attention whatever.

An object of the invention is to provide an accurate, rugged wet bulb thermostat.

The invention will now be described with referenoe to the drawing, of which:

Fig. l is a profile view of one embodiment of a wet bulb thermostat incorporating features of this invention, showing a dripbasin below same;

Fig. 2 is a profile view of the thermostat of Fig. 1, with the thermostat body shown in section, and

Fig. 3 is a plan view looking downwardly upon the thermostat of Figs. 1 and 2.

The thermostat body 5 contains the chamber 6 which is provided for maintaining the proper water level in the device. The chamber 6 receives water under slight pressure through the inlet 1. A portion of this water passes through the passage 8 and enters a second chamber 9. The threaded pipe ID of the special refrigeration fitting I l is screwed into the lower portion of the chamber 9. The refrigeration nut I2 is fitted onto the lower portion of the fitting H and secures the upper end of the leather boot l3 in tight contact within the nut so that it is water tight.

The boot lit in one embodiment of the inven- 5 tion is of tanned sheepskin of uniform density and thickness to ensure uniform Wetting through its entire surface.

The thermometer [4 extends through the compression nut IS, the chamber 9 and into the boot l3 with its bulb I5 near the lower end of the boot. The compression nut I6 is threaded into the thermostat body 5 to hold the thermometer securely in place.

The pipe plug l1 closes the upper portion of the chamber 6.

The funnel-shaped drip basin I8 is mounted below the boot to receive water dripping therefrom and the water is drained to the tracks through the pipe IS.

The bracket is provided for mounting the thermostat in the outdoor air inlet passage.

In operation, a pump circulates water through the inlet 1 into the chamber 6 and out the outlet 4. The outlet 4 is located above the passage 8 so that the water level in the chamber 6 is always above the passage 8 ensuring that at all times, the boot [3 will be full of water.

It is preferred that no pressure be exerted by the pump, -etc., upon the water in the boot and that the only pressure be that from the water head in the'boot and in the chamber 9. This is suificient to cause the Water within the boot to pass to its exterior, so that it may be evaporated by the air passing over it, and is insufficient to force any appreciable excess of water through the boot.

The stem of the thermometer l4 may be provided with the usual electric contacts (not shown) for actuating electric circuits for converting the associated air washer system from evaporative cooling to refrigerative cooling when the wet bulb temperature of the outdoor air rises above a predetermined point, and for converting the system from refrigerative cooling to evaporative cooling when the wet bulb temperature of the air falls below the predetermined point.

Water from the main spray line is usually supplied to the thermostat and in such cases it is necessary to provide a pressure regulating valve in the tubing connecting with the inlet 1 to reduce the pressure of the water entering the chamber 6. When pressure reducing valves are employed, it is desirable to provide an orifice in the inlet or in the tubing connecting with this 55 spirit of the invention.

the excess of Water over that required to replace the volume evaporated at the outer surface of the boot and they could accomplish this whether included in the same or separate bodies.

The thermostat may of course be 'used for reading wet bulb temperatures as well as for actuating controls and may be mounted in reciroulated or conditioned air streams as well as in outdoor air streams. i

While tanned sheep skin has been successfully used for the boot of the thermostat, other porous materials may be used. The term boot is defined herein as a porous receptacle for a thermometer or thermostatic element.

While one embodiment of the invention has been described for the purpose of illustration, it should be understood that the invention is not to be limited to the exact apparatus and arrangement of apparatus described, as many departures and modifications may be suggested to those skilled in the art, without. departure from the What is claimed is: i

1. A wet bulb thermostat comprising a body having a relatively large chamber with substantially vertical walls, one of said walls having a substantially horizontal extension, said extension having an aperture with substantially vertical walls for receiving a thermostatic element and having an aperture with substantially'horizontal walls connecting said first mentioned aperture and said chamber through said one wall, means forming a water inlet into said chamber below said horizontal aperture, a porous boot attached to said extension below said second mentioned aperture and in alignment with said first men said boot, and means forming awater outlet from said chamber above said second mentioned aperture.

2. A wet bulb thermostat comprising a body having a relatively large chamber with substantially vertical walls, one of said Walls having a substantially horizontal extension, said extension having an aperture with substantially vertical walls for receiving a thermostatic element and having an aperture with substantially horizontal walls connecting saidfirst mentioned aperture H and said chamber through said one wall, means forming a substantially horizontal water inlet into said chamber below said second mentioned aperture a porous boot attached to said extension below said second mentioned aperture and inalignmentwith said first mentioned aperture, a thermostatic element extending through said first mentioned aperture in said boot, and means forming a substantially horizontally extending water outlet from said chamber above said second mentioned aperture, said inlet and outlet ex tending through the opposite wall of said chamber to said one wall. 3. A wet bulb thermostat comprising a body having a relatively large tubular chamber .with a substantially vertical axis and with substantially vertical walls, one of. said walls having. a substantially horizontal extension, said extension having an aperture with substantially vertical walls for receiving a thermostatic element and having an aperture with substantially horizontal walls connecting said first mentioned aperture and said chamber through said one wall, means forming a substantially horizontally extending. water inlet into said chamber below said second,

mentioned aperture, a porous leather boot at-.

tached to said extension below said second men'- tioned aperture and in alignment with said first mentioned aperture, a thermostatic element ex-;

tending through said first mentioned. aperture into said boot, and means forming a substantially.

horizontally extending watery'outlet from said chamber above said second mentioned aperture, said inlet and outlet extending through the op.- posite wall of said chamber to said one wall said horizontally extending aperture having a.

diameter substantiallyless than that of said outlet.

CHARLES W. PETERSON. 1 U501"; 

